A New Anthropomorphic Brain Phantom for Multi-Lesion SRS Quality Assurance Testing
Abstract
Purpose
To design an anthropomorphic phantom that closely mimics a clinical brain metastases patient to assess the end-to-end performance of multi-lesion SRS treatments.
Methods
The anthropomorphic phantom resembles a human head and was fabricated using materials to simulate human tissue, bone, and solid tumor targets: high-impact polystyrene, polybutylene terephthalate (PBT), and solid water, respectively. Using a clinical database of patients with multiple brain metastases, key clinical features were chosen for phantom design, including tumor size and spacing. Thermoluminescent dosimeters (TLD) and MD-V3 radiochromic films are used to measure target dosimetry. CT scans were performed to confirm phantom design and feature visualization.
Results
The phantom contains five total targets with three targets being dosimetrically monitored using TLD and film. Positioning and absolute dosimetric differences can be analyzed and reported by comparing the dosimeters measurements and treatment plan. The two remaining non-dosimetric targets provide additional challenge for treatment planning. The solid water targets in the phantom are spheres of 0.5, 1.0, and 1.9 cm diameters representing the median, mean, and relative maximum from a set of clinical patient plans. To allow for single or multi-iso center approaches, the targets are spaced with varying distances from the center of the phantom. Each dosimetric target is approximately 5 cm from each other, and the non-dosimetric targets are greater than 7 cm from the central target. Two PBT inserts are embedded in the forehead and occipital regions of the head, mimicking skull bone. This allows for x-ray-based imaging guidance capabilities.
Conclusion
A multi-lesion SRS anthropomorphic head phantom was designed and created with end-to-end testing capabilities. This phantom helps ensure accuracy for treatment using multi-lesion SRS techniques, particularly with potential use in credentialing for multi-center clinical trials for SRS.